The skin is the first line of defense against external factors, and plays a key role in protecting the body against water loss, pathogens and various harmful environments. Ultraviolet (UV), ionizing radiation, and certain medications or xenobiotics might induce production of ROS and free radicals. Oxidative stress occurs when ROS and free radicals exceed the antioxidant capacity of cells or tissues. Thereafter, ROS and free radicals react with components within the cell (e.g., DNA, proteins, lipids, etc.), thereby resulting in undesired oxidative damage to the skin. It has been reported that ROS and free radicals cause delay of wound healing.
When a wound results from skin damage (such as scald, trauma, surgical injury or contusion), an inflammatory response is triggered at the wound site where a large amount of ROS and free radicals are released to assist immune cells in fighting against the pathogenic bacteria. However, excessive ROS and free radicals might harm the tissues surrounding the wound. During the wound healing process, fibroblasts migrate to the wound site and then proliferate there, thereby resulting in angiogenesis, epithelialization and collagen remodeling. Excessive ROS and free radicals not only inhibit angiogenesis, but also inactivate the enzymes involved in the signaling pathways related wound healing, thereby interrupting wound healing.
Gracilaria sp. and Gracilariopsis sp., are common red algae belonging to Phylum Rhodophyta, Class Florideophyceae, Order Gracilariales and Family Gracilariaceae. These red algae need sufficient illumination to grow up, and mainly reside in the surface layer of seawater (0˜25° C.) in temperate and tropical regions. Since Gracilaria sp. and Gracilariopsis sp. are high in dietary fiber, high in proteins, low in fats, and rich in vitamins, minerals, unsaturated fatty acids, polysaccharides and carotenoids, these two algal species have important economic values. It has been known that Gracilaria sp. and Gracilariopsis sp. may be biologically effective in antioxidation, enhancing immune responses, lowering fats and anti-cancer actions.
It has been reported that the protein extracts from red algae Gracilaria tenuistipitata (GT), which are produced by treating GT with proteinase bromelain and then conducting ammonium sulfate precipitation, have antiradical properties (Jing-Iong Yang et al. (2012), Journal of National Kaohsiung Marine University, 26:43-54).
In spite of the aforesaid, researchers in this field endeavor to look for extracts from other red algae species having useful biological activity.